Were going (hrconto). Picturesque imperfect. It was now dark (skotia hdh egegonei). Past perfect active of ginomai. While they were going, "darkness had already come." And Jesus had not yet come to them (kai ouk elhluqei pro autou o Ihsou). Another past perfect active of ercomai with negative oupw. Darkness had come, but Jesus had not come, while they were going over the sea. The tenses in these verses are very graphic.